JP2013537942A - Paper or paperboard product and method for producing paper or paperboard product - Google Patents

Abstract

The present invention relates to a paper or paperboard product comprising a furnish, wherein the furnish comprises a cationic polymer in an amount greater than 1.5% by weight, an anionic polymer, and microfibrillated cellulose. Or related to paperboard products. The invention further relates to a method for manufacturing said product.

Description

The present invention relates to a paper or paperboard product comprising a furnish comprising a cationic polymer, an anionic polymer, and microfibrillated cellulose.

Background In the papermaking process, there continues to be an interest in finding ways to produce paper or paperboard at a low cost without compromising the properties of the product and without reducing mechanical properties such as product strength. This was done by process optimization or by the use of alternative low cost raw materials, which could gradually replace fairly expensive wood based fibers.

  One way to reduce the cost of a paper or paperboard product is to increase the filler content of the product, thereby reducing the amount of fiber used in the paper or paperboard. In addition to being economically beneficial, the filler also improves the opacity and printability of the product. However, it is necessary that the cost of the filler is substantially lower than the cost of the fiber material. Also, a large amount of filler in the product reduces the strength. Therefore, there is a balance between the amount of filler that can be added and the required strength of the paper or board to be produced.

  In addition, during the manufacture of paper or paperboard, it is desirable to produce a strong but low density product. Increasing the strength of the paperboard usually increases the density. On the other hand, when the density is decreased, the strength usually decreases. Thus, there is a balance between the desired strength and density of the paperboard product.

  For example, the loss of strength caused by the addition of large amounts of filler or by increased bulk is compensated by improving the fiber bonding properties between the fibers of the paper or paperboard and thereby maintaining the strength. It is possible. A powerful treatment to improve the strength of paper or paperboard, especially dry strength, has heretofore been to add a strength agent, preferably cationic starch, to the furnish prior to the sheet forming operation. Met. Cationic starch molecules added to the furnish adhere to the inherently anionic pulp fibers by electrostatic attraction or by hydrogen bonding, thereby being retained in the wet fiber mat and remaining in the final paper or paperboard be able to. In order to achieve the same effect, amphoteric starches and even anionic starches can be used.

  When a large amount of cationic starch is added to a papermaking furnish, two main problems arise in achieving high strength of paper or paperboard. The first problem is that the cationic starch molecules tend to occupy or shield the anionic charge on the cellulose fiber, thereby limiting the amount of cationic starch that can be anchored to the fiber. If an excess of cationic starch is added, only a portion of the added starch will be retained in the sheet and the remainder will circulate in the white water system of the paper or board machine. The second problem is that fibers made cationic by the extra addition of cationic starch adsorb other cationic additives such as sizing agents and retention aids that are commonly added to pulp slurries. It becomes impossible. In addition, high starch levels often cause problems with runnability, microorganisms, and foaming during the manufacturing process, which has the ability of the fiber to absorb / adsorb starch molecules (a certain capacity). Is partly related.

  Another approach to using starch to improve dry strength is to add uncooked starch or partially cooked starch. In this way, the starch is gelatinized in the wet end papermaking process, pressing and drying sections. In addition to the physicochemical characteristics in the unheated or partially heated form, it has a better tendency to both improve retention and anchor to fiber-fiber bonds.

  Another way in which the amount of starch in the paper or paperboard product can be increased is to alternately add cationic starch and anionic polymer to the furnish. In this way, a multilayer of polyelectrolyte can be formed and the amount of starch can be increased. This is described, for example, in WO2006 / 041401. However, these multilayer concepts, i.e., layer-by-layer adsorption techniques or polymer complexation, are particularly important at the mill scale in order to obtain sufficient strength and retention levels. Is needed, it is quite difficult to implement. This type of concept is very sensitive to polymer concentration, order of addition, polymer and system charge density, temperature competitive adsorption, dissolved colloidal material, and dose.

  When some polymers are added, it is preferred that polymer complexation occurs on the fiber surface. To achieve this, it is important that all polymers be anchored to the fiber surface, otherwise anion-cationic polymer complexation can occur in the liquid phase, which is May negatively affect the driving performance. If retention is not high, especially when using polymers derived from renewable resources, the impact on microbial activity at the wet end may be very significant. In this respect, it is preferred that the adsorption of all anionic-cationic polymer additives is well controlled.

  In making paper or paperboard products with good strength properties, there remains a need for robust systems with high polymer retention.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a paper or paperboard with improved strength, maintained density, and further reduced.

  Another object of the present invention is to provide a method that can produce paper or paperboard with improved strength, density maintained, and even reduced in an easy and cost effective manner.

  Yet another object of the present invention is to ensure high load of the cationic polymer to the paper or paperboard without compromising retention of the added polymer.

  These objects and other advantages are realized by the paper or paperboard product according to claim 1. The present invention is a paper or paperboard product comprising a furnish comprising a cationic polymer and an anionic polymer, wherein the furnish further comprises microfibrillated cellulose and the amount of cationic polymer is the total furnish. It relates to a paper or paperboard product which is more than 1.5% by weight with respect to the weight. Products made from furnishes containing cationic polymers, anionic polymers and microfibrillated cellulose (MFC) are shown to have increased strength as the amount of cationic polymer can be increased. It was. Furthermore, it has been shown that even if the strength of the product is increased, the density of the product is not increased as expected. Thus, it is possible to produce a product with reduced bulk but still very good strength properties.

  The furnish preferably comprises cellulosic fibers, which can be hardwood and / or softwood fibers.

  The furnish preferably contains 1-30% by weight (based on the total weight of the furnish) of microfibrillated cellulose. The amount of cationic polymer, anionic polymer, MFC in the product depends on the desired properties of the product and the end use of the product. A higher amount of cationic polymer increases the strength of the product, but the combination of MFC, anionic polymer, and cationic polymer indicates that the product can retain a higher amount of cationic polymer. It was done.

  The cationic polymer is preferably cationic starch or amphoteric starch. The anionic polymer is preferably carboxymethylcellulose (CMC).

  The product can be a multilayer product having at least two layers of paper or paperboard. It may be preferred that the product comprises at least three layers and that the layer located in the middle of the product comprises a furnish comprising a cationic polymer, an anionic polymer and microfibrillated cellulose.

  The present invention is further a method of manufacturing a paper or paperboard product comprising the steps of providing a furnish comprising fibers and more than 1.5% by weight of the furnish (based on the total weight of the furnish) Adding a cationic polymer of: an anionic polymer to the furnish; adding a microfibrillated cellulose to the furnish; and then the finished paper to form a web And a step of subjecting the wire to a wire.

  It is preferred to add 1-30% by weight (based on the total weight of the furnish), more preferably 1-15% by weight of microfibrillated cellulose to the furnish.

  Preferably, the cationic polymer, anionic polymer, and MFC are added separately to the furnish. First, a cationic polymer is added to the furnish in the first step, MFC is added in the second step after the first step, and anionic in the third step after the second step. It is preferable to add a polymer. It is preferred that the cationic polymer be added to the furnish in one step, i.e., at a single addition point. It is also preferred to first mix the cationic polymer and the microfibrillated cellulose, then add the mixture to the furnish, and then add the anionic polymer to the furnish. This method has been shown to be able to increase the strength without adversely affecting the bulk.

DETAILED DESCRIPTION The present invention relates to a paper or paperboard product comprising a furnish comprising a cationic polymer, an anionic polymer and microfibrillated cellulose. The furnish comprises a cationic polymer, preferably cationic starch or amphoteric starch, greater than 1.5% by weight (based on the total weight of the furnish), preferably greater than 2.0% by weight, even more preferably 3%. In an amount greater than 0.0% by weight. Thus, a paper or paperboard product made from a furnish or a layer of paper or paperboard product also contains a cationic polymer in an amount greater than 1.5% by weight. It may be possible to increase the amount of cationic polymer retained in a product made from the furnish by adding a cationic polymer, an anionic polymer, and microfibrillated cellulose to the furnish. Indicated. For furnishes, and also for paper or paperboard products, increasing the amount of cationic polymer such as starch increases the strength of the product. Both z-strength and Scott-Bond and compressive strength have been shown to increase for products made according to the present invention. Furthermore, the density of the product does not decrease as worried, and therefore it is possible to produce very strong but still high bulk paper or paperboard products.

  One reason for improved retention of polymer and MFC added to the furnish is the formation of relatively large particle polymer composites. The composite formed in accordance with the invention is much larger compared to polymer composites formed with prior art PEM technology. Microfibrillated cellulose forms a composite with the polymer used in the present invention, both of which are attached to the fiber by bonding and due to the relatively large size, thereby holding the composite in the fiber matrix Will come to be. When retention is improved, few BOD and COD problems in white water are caused.

  In addition, the fiber charge of the treated furnish can be adjusted and controlled to ensure that the fiber is anionic. Similarly, the total charge of the system can be adjusted and controlled. Because fibers are usually anionic, commonly used paper additives and chemicals are designed to work with anionic fibers. Thus, there is the advantage that the charge of the fiber can be controlled to make the fiber anionic, thereby allowing the use of commonly used papermaking additives.

  The furnish preferably comprises cellulosic fibers. The cellulosic fibers may be hardwood and / or coniferous fibers. Cellulosic fibers can be mechanically, chemically mechanically and / or chemically treated. The fibers may also be bleached or unbleached. The furnish can also contain broken or recycled paper or paperboard. The furnish may also contain fibers derived from non-wood based materials.

  Microfibrillated cellulose contains many negatively charged “sites” and a large amount of open surfaces that are formed during the manufacture of MFC. Thus, the addition of microfibrillated cellulose to the furnish will increase the sites where the cationic polymer can adhere. Thus, by combining the addition of microfibrillated cellulose and a cationic polymer, it is possible to increase the amount of cationic polymer retained in the fiber and hence also in the paper or paperboard product. In addition, anionic polymers are added, among other things, to ensure that the furnish fibers are anionic after the addition of the cationic polymer and MFC. Anionic polymers also of course bind cationic polymers. Anionic or cationic polymers and MFC added to the furnish interact with each other, thereby allowing larger amounts of polymer and MFC to adhere to the fibers, thereby increasing the strength of the final paper or paperboard product. .

  Cationic polymers include cationic starch, amphoteric starch, polyvinylamine, chitosan, primary and secondary amines, polyethyleneimine, polyDADMAC, polyallylamine, cationic polysaccharide, PVAm, polyethyleneimine (PEI), polyethylene oxide ( PEO), polyamine, polyvinylpyrrolidone, modified polyacrylamide (PAM), or one or more selected from the group consisting of similar polymers. The cationic polymer is preferably a cationic starch, which results in a board or paper with improved strength properties, which is advantageous because it is economically beneficial due to its low price and availability.

  Anionic polymers include carboxymethylcellulose (CMC), polyvinyl sulfate, anionic galactoglucomannan, anionic starch, polyphosphoric acid, alginate polyacrylic acid, protein, anionic polyacrylamide, anionic silica, bentonite, It can be one or more selected from the group consisting of alum for papermaking and polymethacrylic acid. The anionic polymer is preferably CMC. This is because it interacts well with the cationic polymer and is economically beneficial due to its low cost. The anionic polymer is preferably added in an amount such that the furnish fibers have the same charge as before the chemical is added, ie, return to the original charge of the fibers.

  The ratio between added cationic starch and anionic CMC is preferably 5: 1 to 15: 1, preferably 10: 1. If other polymers are used, this ratio may be different, for example between 5: 0.1 and 30: 0.1 (cationic polymer: anionic polymer). The optimum ratio depends on the charge difference of the added polymer. In order to obtain the optimal strength and density of the paper or paperboard product, the ratio between the cationic and anionic polymers added to the furnish is controlled and adjusted.

  One advantage of the present invention is that an amount of cationic polymer in excess of 1.5% by weight can be added to the furnish in a single addition step. This is thanks to the combination of cationic polymer, anionic polymer and MFC. This can be compared to the polyelectrolyte multilayering technique (PEM) described in the prior art, where a small amount of cationic polymer is added in a consecutive step. The present invention provides a more robust and less complex method of producing paper or paperboard products that contain a high amount of cationic polymer.

  However, it is also possible to add each of the components, ie the cationic polymer, the anionic polymer, and the MFC in multiple sequential steps. Thus, the cationic polymer is added in multiple steps, ie, at least two smaller amounts of cationic polymer are added to the furnish, preferably in sequential steps. The same can be done for anionic polymers and MFC if desired.

  Microfibrillated cellulose (MFC) (also known as nanocellulose) is a material made from wood cellulose fibers or agricultural raw materials or wastes, whose individual microfibrils are partially or Fully detached from each other. MFCs are usually very thin (˜20 nm) and the length is often between 100 nm and 10 μm. However, microfibrils can also be longer, for example, between 10 and 100 μm, but lengths up to 200 μm can be used. Fibers that are fibrillated and have microfibrils on the surface, and microfibrils that are separated and present in the aqueous phase of the slurry are included in the definition of MFC.

  The MFC can be manufactured in several different ways. Cellulosic fibers can be mechanically processed so that microfibrils are formed. The production of nanocellulose or microfibrillated cellulose using bacteria is another option. Electrospinning is another method for producing microfibrillated cellulose or nanofibers. It is also possible to produce microfibrils from cellulose using various chemicals and / or enzymes that break or dissolve the fibers. Another option is to use water vapor and pressure to break hydrogen bonds within and between fibrils. Most commonly, MFCs are manufactured by combining chemical or biochemical steps with one or several steps of mechanical pre-treatment or post-treatment.

  An example of the production of MFC is shown in WO2007091942, which describes the production of MFC by beating combined with enzyme addition.

  It is also possible to modify the microfibrillated cellulose before adding it to the furnish. In this way it is possible to change the interaction and affinity for other substances. For example, increasing the stability of MFC fibrils and fibril aggregates by introducing more anionic charges into the MFC. How the modification of the microfibrillated fibers takes place depends, for example, on other components present in the furnish.

  It is also possible to add highly beaten pulp to the furnish. Therefore, cellulosic pulp beaten to an SR value of> 80 can be used. It is possible to use a fraction containing beaten pulp with an SR value> 80, for example a fines fraction. It may be preferred to use CTMP pulp beaten to an SR value of> 80. It is possible to beat the entire CTMP pulp in order to use the fraction of the beaten CTMP pulp with an SR value> 80. In order to achieve the same strength effect as compared to the case of adding MFC, it may be necessary to increase the amount of highly beaten pulp added to the furnish. On the other hand, when highly beaten pulp is added, densification is reduced.

  The chosen amount of cationic polymer, anionic polymer, or MFC added to the furnish depends on the final product to be produced and the desired properties of the product. A large amount of cationic polymer increases the strength of the product. However, the amount of cationic polymer cannot be increased excessively as other problems can occur. For example, if the amount of cationic polymer, such as cationic starch, is too high, the paper or paperboard product may become sticky, which may make it difficult to remove the paper or paperboard web from the wire. If the amount of MFC is too high, the density of the paper or paperboard product may increase too much. This may be disadvantageous, for example, when making high quality paperboard that often needs to have a high bulk. In addition, MFC is a very fine material that readily absorbs water, and increasing the content makes the product more difficult to dehydrate, so too much MFC can cause dehydration problems. If the amount of anionic polymer is too high, the added anionic polymer will not be able to bind to the cationic polymer, fibers with cationic charge and / or MFC. Accordingly, free amounts of anionic polymer are present in the furnish, which may make it difficult to dehydrate the furnish to form a fiber-based web. .

  The paper or paperboard product is preferably a multi-layer product comprising at least two papers of paper or paperboard. It may be preferred that the product has at least three layers and that the centrally located layer of the product comprises a furnish comprising a cationic polymer, an anionic polymer and microfibrillated cellulose. It is also preferred that the furnish comprises CTMP and it forms the central layer of the paper or paperboard product. However, it is also possible that at least one outer ply of the product, as well as all layers of the product, comprise a furnish comprising a cationic polymer, an anionic polymer and MFC. In some products, it may be advantageous for at least one of the outer layers to include a furnish comprising a cationic polymer, an anionic polymer, and MFC. In this way it is possible to increase the strength and / or bulk of this layer. Thus, depending on the end use of the product, it is determined which and how many layers will contain the furnish containing the cationic polymer, the anionic polymer and MFC.

  It is not necessary for the entire furnish in the layer of the paper or paperboard product to contain a cationic polymer, an anionic polymer and MFC, but the cationic polymer, anionic polymer and MFC are the majority of the furnish in the layer. It is preferable to add. However, the layer may also contain other components, such as broken pulp, that do not contain a cationic polymer, an anionic polymer and MFC.

  The furnish can also contain various amounts of fillers, for example, to increase process operability and cost efficiency, and to increase the substrate produced. Other commonly used additives used in the manufacture of paper or paperboard can also be added.

  The paperboard product is preferably a high quality paperboard product such as a liquid packaging board, a graphic board, or a food business board. The paper product is preferably high quality paper such as grade A or B copy paper, graphic paper, LWC, SC, or newsprint for high speed printers. However, other grades such as cardboard and liners can be produced.

  Products according to the invention, ie products made from a furnish treated with a cationic polymer, MFC and an anionic polymer, provided that the furnish comprises at least 1.5% by weight of a cationic polymer, are preferably A paperboard with increased strength and little or no densification. The paperboard is preferably a multi-layer board, and a furnish comprising a cationic polymer, an anionic polymer and MFC forms at least one layer of the product, and the board is preferably more than 250 kPa Z-strength, preferably between 250 kPa and 400 kPa, even more preferably between 250 kPa and 350 kPa, and its formation between 300 kg / m3 and 550 kg / m3, preferably between 350 kg / m3 and 500 kg / m3 Having the density of the layer. The central layer of the paperboard product preferably has a z-strength of greater than 250 kPa, and the z-strength of the paperboard product is also greater than 250 kPa, since the central layer of a multilayer paperboard product is usually the weakest layer.

  The present invention further provides a method for producing a paper or paperboard product comprising the steps of providing a furnish comprising fibers, and adding a cationic polymer in an amount greater than 1.5% by weight to the furnish. A method comprising: adding microfibrillated cellulose to the furnish; adding an anionic polymer to the furnish; and subjecting the furnish to a wire to form a web. The addition of cationic polymer, anionic polymer, and MFC is preferably done in a machine chest or prior to a fan pump. It is also possible to add the components to the circulating water that is later added to the furnish. However, as long as there is sufficient time to mix the cationic polymer, anionic polymer, and MFC with the furnish before subjecting the furnish to wire, the practical use of the cationic polymer, anionic polymer, and MFC All the points of addition can be used.

  Preferably, the cationic polymer, anionic polymer, and MFC are added separately. Also, first, in the first step, the cationic polymer is added to the furnish, MFC is added in the second step after the first step, and the third step is followed by the third step. It is also preferable to add an anionic polymer in the step. First, it is preferred to add the cationic polymer to the furnish, which will adsorb to the furnish fibers. Thereafter, MFC is added and the free MFC will adsorb to the added MFC. The anionic polymer is finally added to adsorb the unadsorbed cationic polymer (if any) of the furnish and, among other things, to bring the total charge of the furnish back to negative. Since many papermaking additives are cationic and therefore interact well with the anionic fibers of the furnish, it is preferred that the fibers have a negative charge.

  Preferably, the furnish is mixed between each addition point, i.e. before adding another component. It is preferred to add the cationic polymer to the furnish in one step, ie at the point of one addition.

  It is also possible to mix the cationic polymer, anionic polymer, and / or MFC before adding it to the paper furnish. Therefore, it is possible to add all three components after mixing them. However, it is also possible to mix two of the components, add the mixture to the furnish, and then add the third component. It is preferred to mix the cationic polymer and MFC and add it to the furnish before adding the anionic polymer or mixing the anionic polymer and MFC and then adding the cationic polymer.

Example Materials used:
500 CSF Chemo thermo mechanical pulp (CTMP).

  Microfibrillated cellulose (MFC) was made by beating a 4% consistency bleached softwood kraft pulp to 28SR using an edge load of 2 Ws / m. Thereafter, the pulp was subjected to an enzyme treatment using an endoglucanase (Novozym 476) having an activity of 0.85 ECU / g. The enzyme was put into the pulp and then treated at 50 ° C. for 2 hours at pH 7. After the enzyme treatment, the pulp was washed and the enzyme was inactivated at 80 ° C. for 30 minutes. Thereafter, the pulp is beaten once more to 90-95 SR, and then the beaten pulp is fluidized (Microfluidizer, Microfluidics corp.) By passing 3% consistency pulp through a 400 μm chamber and then a 100 μm chamber. ) To form the MFC used.

  The starch used was cationized starch, Raisamyl 70021, Ciba (currently BASF).

  The CMC used was FinnFix30, CP-Kelco.

  The C-PAM used was Percol 292 NS, Ciba (currently BASF).

  The BMA used was Eka NP495, Eka Chemicals.

procedure:
The dried CTMP was immersed in water overnight and then dispersed in hot water. Thereafter, the CTMP suspension was diluted to a concentration of 0.3%.

  The produced MFC was also diluted to a concentration of 0.3% and dispersed using a kitchen mixer.

  Test sheets were prepared using a formette sheet former. Sheets were made according to the following procedure; the pulp suspension weighed to produce 150 gsm sheets was added to the stock tank. During stirring, cationic starch was added in the order mentioned if cationic starch was used, MFC if MFC was used, and CMC if CMC was used. Here, 30-60 seconds were added between each addition to ensure complete mixing before the next component was added. After 30 seconds, 500 g / t C-PAM was added to the stock, and after another 30 seconds, 300 g / t BMA was added, after which sheet formation was started.

  The formed sheet was wet-pressed and dried while suppressing shrinkage. The dried sheets were tested for structural density according to SCAN P88: 01 and z-strength according to SCAN P80: 88.

  As can be seen from Table 1, the strength of Samples 1 and 2 with the addition of starch, CMC, and MFC is increased compared to the case without MFC. Also, the density of the board is almost maintained, i.e., hardly increased.

  In view of the above detailed description of the invention, other modifications and variations will become apparent to those skilled in the art. It will be apparent, however, that other such modifications and variations can be made without departing from the spirit and scope of the invention.

Claims (14)

  A paper or paperboard product comprising a furnish comprising a cationic polymer and an anionic polymer, wherein the furnish further comprises microfibrillated cellulose and the amount of cationic polymer is greater than 1.5% by weight (finished paper Paper or paperboard product, characterized in that it is based on the total weight of the material.   The paper or paperboard product according to claim 1, wherein the furnish comprises cellulosic fibers.   Paper or paperboard product according to claim 1 or 2, characterized in that the furnish comprises 1 to 30% by weight of microfibrillated cellulose.   4. Paper or paperboard product according to any one of claims 1 to 3, characterized in that the cationic polymer is cationic starch or amphoteric starch.   The paper or paperboard product according to any one of claims 1 to 4, characterized in that the anionic polymer is carboxymethylcellulose (CMC).   6. A paper or paperboard product according to any one of the preceding claims, characterized in that it is a multilayer product comprising at least two paper or paperboard layers.   7. Paper according to claim 6, characterized in that the product comprises at least 3 layers, the layer located in the middle of the product comprising a furnish comprising a cationic polymer, an anionic polymer and microfibrillated cellulose. Or paperboard.   The product is a multi-layer board, and the furnish comprising a cationic polymer, an anionic polymer and MFC forms at least one layer of the product, the board has a z-strength of 250-400 kPa, and 300- 8. Paper or paperboard according to any one of the preceding claims, characterized in that it has a density of the formed layer between 550 kg / m3. A method of manufacturing a paper or paperboard product comprising:
-Preparing a furnish containing fiber;
-Adding more than 1.5 wt% cationic polymer to the furnish;
-Adding microfibrillated cellulose to the furnish;
-Adding an anionic polymer to the furnish;
Subjecting the furnish to a wire to form a web.   The process according to claim 9, characterized in that 1 to 30% by weight of microfibrillated cellulose is added to the furnish.   The process according to claim 9 or 10, characterized in that the cationic polymer, the anionic polymer and the MFC are added separately to the furnish.   First, a cationic polymer is added to the furnish in the first step, MFC is added in the second step after the first step, and anionic in the third step after the second step. 12. A method according to any one of claims 9 to 11, characterized in that a polymer is added.   13. A method according to any one of claims 9 to 12, characterized in that the cationic polymer is added at a single addition point.   14. Any one of claims 9, 10 or 13, characterized in that the cationic polymer and the microfibrillated cellulose are added to the furnish after mixing and then the anionic polymer is added to the furnish. The method according to item.